1. Field of the Invention (Technical Field)
The present invention relates to an apparatus for exerting a force on a load, comprising at least a first spring system and a second spring system, which two spring systems are coupled with the load and produce forces that are applied to the load, wherein an adjusting device is provided coupled with the load, which is equipped with at least one coupling with which the first spring system and/or the second spring system are/is coupled, and which adjusting device is designed for moving the coupling subject to an adjustment of the load.
2. Description of Related Art
Such an apparatus is known from the German patent application DE-A-34 06 669.
Such an apparatus is also known from the British patent specification GB-A-489 547. The apparatus known from the British patent specification GB-A-489 547 is illustrated by applying it to a load in the form of a drawing board or canvas that needs to be adjustable in height smoothly and with little effort. To this end the drawing board is at one side coupled with a first spring system having a substantially vertical orientation. The drawing board is further coupled with a zigzag construction, tensioning substantially horizontally oriented springs that form the second spring system. The coupling of the first spring system and the second spring system with the drawing board, in connection with the zig-zag construction that forms the adjusting device, is designed such that the springs of the two spring systems, where they engage the drawing board, generate substantially self-compensating forces.
The apparatus known from the British patent specification GB-A-489 547 has several drawbacks. For example, the known apparatus prescribes the use of so-called zero-free-length springs, whose spring force is proportional to the total length of the spring. Such springs are relatively expensive compared with standard springs, whose spring force is proportional to the extension of the spring.
A further drawback of the apparatus known from the British patent specification GB-A-489 547 is that it takes up a rather large amount of space owing to the horizontally oriented springs requiring sufficient extension space.
The apparatus according to DE-A-34 06 669 is embodied with the first spring system having a linear spring characteristic and being coupled with the load, and having the second spring system coupled with the coupling at a side of the coupling remote from the load, and the coupling being designed for adjusting the second spring system subject to a predetermined spring characteristic of the second spring system such that, at the side of the load, the combination of the coupling with the second spring system possesses a force path diagram having a predetermined characteristic.